An experimental investigation of the interaction of water waves with flexible structures acting as breakwaters was carried out. Wave profiles, mapped out by water level measuring transducers, were studied to provide information on the performance of different breakwater models. A new signal analysis procedure for determining reflection coefficients based on wavelet theory was developed and compared to a conventional method. The reliability of using wavelet analysis to separate a partial standing wave into incident and reflected wave components was verified with a numerical example. It was also verified by the small variance in the estimates of the incident wave height from independent experimental measurements. Different geometries of rigid and flexible structures were constructed and examined. Reflection, transmission and energy loss coefficients were obtained over them. The influence of various properties of the models, such as the width and the internal pressure, on the effectiveness in reflecting or absorbing the incident wave energy was determined. Various factors which affect the performance of the breakwater, including the water depth, the wave length and the wave amplitude, were measured and documented. Suspended and bottom-mounted models were considered. The flow field over and near a hemi-cylindrical breakwater model was also examined using a flow visualization technique. An overall comparison among the models has also been provided. The results showed that the rectangular models, rigid and flexible, are the most effective structures to dissipate wave energy. The flow visualization technique indicated that the flow conforms with the circular geometry of a hemi-cylindrical breakwater model, yielding no flow separation. / Ph. D.

Solving for energy losses in pipe junctions has been a focus of study for many years. Although pipe junctions and fittings are at times considered "minor losses" in relation to other energy losses in a pipe network, there are cases where disregarding such losses in flow calculations will lead to errors. To facilitate these calculations, energy loss coefficients (K-factors) are commonly used to obtain energy losses for elbows, tees, crosses, valves, and other pipe fittings. When accurate K-factors are used, the flow rate and corresponding energy at any location in a pipe network can be calculated. K-factors are well defined for most pipe junctions and fittings; however, the literature documents no complete listings of K-factors for crosses. This study was commissioned to determine the K-factors for a wide range of flow combinations in a single pipe cross and the results provide information previously unavailable to compute energy losses associated with crosses. To obtain the loss coefficients, experimental data were collected in which the flow distribution in each of the four cross legs was varied to quantify the influence of velocity and flow distribution on head loss. For each data point the appropriate K-factors were calculated, resulting in over one thousand experimental K-factors that can be used in the design and analysis of piping systems containing crosses.